This invention relates to devices with displays and, more particularly, to control of display brightness.
Devices which include displays come in a variety of packages. Notebook computers, personal digital assistants, cellular phones, hand-held computers, camcorders, and cameras are but a few of the devices which may include displays.
Particularly for mobile products, a user may potentially view the display in a broad range of environmental, or ambient, illumination conditions. Since the eyes adapt to the ambient luminance, a change in the environment may result in the display no longer being readable. For example, some mobile products use a liquid crystal display (LCD) that is readily visible in bright ambient lighting conditions, but operates using a backlight for dim surroundings.
The inability to see the display may present problems for the user. For example, there may be environments where the display is too bright to view comfortably as well as environments where the user is unable to see any display information. In the latter situation, the user may conclude that the product is non-functional. Further, since the ability to perceive color and contrast are a function of luminance, the failure to maintain display brightness may cause display information to be unperceivable.
A common technique is to provide the viewer with a manual control to adjust the display brightness. For some mobile products, such as notebook computers, having a manual adjustment may be adequate. For other products, such as personal digital assistants (PDAs), adjusting the display brightness may become problematic, as the PDA may be moved frequently from place to place.
Other devices, such as some of the newer portable web browsers, use microdisplays with magnifying optics. These devices generally require the user to look into an eye piece. Because ambient light is not illuminating the display surface, these devices must be luminous in order to be seen.
For all of these devices, an automatic brightness adjustment would make the devices easier to use. Thus, a need exists for a way to automatically adjust the brightness of displays.